Transcriptional Repression of Hox Genes by C. elegans HP1/HPL and H1/HIS-24

Elucidation of the biological role of linker histone (h1) and heterochromatin protein 1 (hp1) in mammals has been difficult owing to the existence of a least 11 distinct h1 and three hp1 subtypes in mice. caenorhabditis elegans possesses two hp1 homologues (hpl-1 and hpl-2) and eight h1 variants. remarkably,one of eight h1 variants,his-24,is important for c. elegans development. therefore we decided to analyse in parallel the transcriptional profiles of his-24,hpl-1/-2 deficient animals,and their phenotype,since hpl-1,hpl-2,and his-24 deficient nematodes are viable. global transcriptional analysis of the double and triple mutants revealed that hpl proteins and his-24 play gene-specific roles,rather than a general repressive function. we showed that his-24 acts synergistically with hpl to allow normal reproduction,somatic gonad development,and vulval cell fate decision. furthermore,the hpl-2; his-24 double mutant animals displayed abnormal development of the male tail and ectopic expression of c. elegans hom-c/hox genes (egl-5 and mab-5),which are involved in the developmental patterning of male mating structures. we found that hpl-2 and the methylated form of his-24 specifically interact with the histone h3 k27 region in the trimethylated state,and his-24 associates with the egl-5 and mab-5 genes. our results establish the interplay between hpl-1/-2 and his-24 proteins in the regulation of positional identity in c. elegans males. © 2012 studencka et al.